Arbitrary precision decimal

[ThomasdenH]

Beancount has a specific system for dealing with precision, but it can handle arbitrarily large precision. Currently this crate uses rust_decimal, which has a 128 bit integer under the hood. However, that's insufficient for real world applications like cryptocurrency balances. It is of couse possible to lower the precision for transactions, but this as the link argues, this is not ideal. It can also create rounding errors that cause balance statements to fail later on (as I've dicovered).

So I'd like to move to an arbitrary precision decimal, or at least give users that option. I've not found 1.0.0 crates that do this, but I've found:

• bigdecimal
• fraction